There’s something about Barack Obama that induces Americans to imagine what they cannot see. The right envisions a vile socialist, while many on the left picture an inspired liberal, politically restrained in his first term but now free to pursue his true beliefs.

No hard evidence exists to sustain either view. Obama behaves like a centrist who leans tentatively left on certain social programs but boldly right on military force and civil liberties. His supporters, who have watched him duplicate and codify some of the Bush administration’s most damaging civil liberties violations, are now reduced to wishful thinking that an authentic Obama will soon step forward and return the country to the constitutional footing that was abandoned after 9/11.

After all, this reasoning goes, he taught constitutional law at the University of Chicago, a credential he used to denounce George W. Bush at a 2007 fundraiser: “I was a constitutional law professor,” he was quoted as saying, “which means unlike the current president I actually respect the Constitution.”

Let us suppose that this respect for the Constitution, dormant during Obama’s first term, can be revived during his second. In that fanciful spirit, it is easy to compile a wish list of actions he might take, either by using his executive authority alone or by campaigning hard for Congress to reconsider portions of the Patriot Act, the amended Foreign Intelligence Surveillance Act, the use of military commissions and other measures. Since his re-election, however, he has done the opposite. In late December, he signed a five-year extension of FISA’s broadened surveillance powers without endorsing even the weakest requirements, which were voted down in the Senate, to keep Congress informed of rulings by the secret FISA court, and to report whether domestic communications had been intercepted.

The trouble is the country’s state of mind. Giving up invasive counterterrorism tools still seems risky, and Obama’s interest in risk-taking lies elsewhere. In civil liberties, he does not try to shape the popular mood; instead, he succumbs to it.

“I think what the president should be supporting,” says Susan Herman, president of the American Civil Liberties Union, “is the idea that it is now time to take an empirical look” at the extraordinary measures enacted in the wake of 9/11, to appraise their dollar costs and effectiveness, “instead of just assuming by inertia that we should just be doing the same thing.” Early assumptions have proved misguided, Herman believes: hunting down charities with alleged ties to terrorism in order to disrupt their flow of funds has had little impact, for example, and the vast, expensive surveillance mechanism has been counterproductive, leaving intelligence analysts “drowning in data.”

So at a cash-conscious moment in Washington, Herman makes a canny fiscal argument to question “the entire apparatus under the Patriot Act,” which is so secretive that “we don’t really know if we’re spending money in the right place.”

Even if a second-term Obama were inclined to work his way through an ambitious labyrinth of reforms, he might be impeded by the slow pace of history. In past episodes, the country has taken time to recover its balance after a spasm of fear. Only with the perceived threat gone and the egregious abuses exposed have courts ruled wisely and Americans looked back with shame on what they’d done. Judging by earlier deviations from constitutional protections in the name of national security, the conditions may not yet be ripe for the post-9/11 “war on terror” to release its grip on the Constitution.

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Five previous eras are instructive. The first four concluded following their respective wars: the political prosecutions under the 1798 Alien and Sedition Acts during the virtual war with France; the suspension of habeas corpus in the Civil War; the use of the Espionage Act of 1917 and the Sedition Act of 1918 to persecute dissenters during World War I; and the internment of ethnic Japanese citizens during World War II. It was only after the sense of danger had ended that the judicial and legislative branches stood taller.

But will the danger of terrorism end—and if so, how? Certainly not with a clear victory or a treaty. In other countries at other times, it has faded gradually as the circumstances have shifted. And here, now? Perhaps if terrorism slowly declines, Americans will eventually notice its absence, and an evolving sensation of security will open the country to a reassessment of the post-9/11 measures. That was the pattern of the first four historical deviations.